Field of the Invention
The present invention relates to mobile devices such as mobile terminals and to communication control methods for such devices sending and receiving information using a plurality of TCP connections.
Description of the Related Art
Transmission Control Protocol (TCP) is known as a typical protocol used for communication that demands reliability, such as the sending and receiving of files (see RFC 793: Transmission Control Protocol (http://www.ietf.org/rfc/rfc793.txt)). Using a plurality of TCP connections is one method for increasing the speed of communication. This method typically divides the data to be sent into a plurality of pieces and sends the pieces in parallel over a plurality of TCP connections. This method is known as being highly effective in cases where the physical communication channel between information terminals has sufficient bandwidth. Such use is also being considered in wireless environments (see Japanese Patent Laid-Open No. 2010-67015).
Such a method of using a plurality of TCP connections can be considered effective, with no major disadvantages, when the communication environment is stable and the information device is a standard device that does not run on batteries. However, the communication speeds become unstable for wireless information terminals, due to the terminals typically being several kilometers or more away from a base station, frequently switching between base stations that are in range when the terminal is moving at high speeds, the terminal receiving weak signals within buildings, and so on. Accordingly, a method that uses a plurality of TCP connections has been problematic in that such a method is not simply ineffective, but that in some cases, using a single TCP connection actually provides higher communication speeds.
There is a further problem in that mobile terminals run on batteries, and a method that uses a plurality of TCP connections employs a plurality of CPU cores, which can affect the time for which the terminal can be run.